Esther Inglis-Arkell

We're constantly being told how terrible our hearing and sense of smell are, compared to other animals. Perhaps that's why we rely on our eyes. But there are plenty of times when our eyes deceive us, even when our other senses are telling us the truth.

When you're believing your lying eyes instead of your truthful ears, you're falling victim to the Visual Capture Illusion. Find out how it can lead you astray, below.

When I say the word, say, "apple," what do you think of? Do you imagine the smell of apples at a grocery store? Or in a pie? Do you flash on the taste, the sound that apples make when you bite into them, or the feel of an apple in your hand? Most likely, no. If you go into it in any detail, it's generally to visualize an apple. Humans are, for the most part, guided by our eyes. Our other systems are there for confirmation or as early warning systems, but they are secondary to our understanding of the world. This willingness to put our other senses in second place can lead us to make some errors.

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The tendency to let sight take precedence when forming a picture of the world around us is called visual capture. So what problems, exactly, could that cause?

Let me start out with a little anecdote from my life. A train line runs just down the street from my place. One day, when I was a little tired, I heard the train. I was looking to the left, and saw a train coming from a few blocks away, and knew it was going to stop at least once before it got to where I was. I began to cut across the street — and then I looked to the right. The train running in the other direction was only half a block away, and going full speed. Now that I saw the train coming from the other direction, it was clear that the train I had heard was far closer than several blocks away. But my eyes saw a faraway train, and my brain went, "Well, I suppose that's just how trains sound now," and nearly walked me into the path of an oncoming train. This actually happens quite frequently, and people are killed that way. The ears know better, but when visual information is given for a likely enough explanation, the brain just forms a picture based on what the eye sees.

There are illusions that rely on this. One of them is used by ventriloquists and puppeteers all the time. When's the last time someone talked to you, and you turned your head and stared a foot and a half to the right of them, assuming their voice was coming from there? And yet we do just that, when a ventriloquist comes on stage. The audience, for the most part, can hear where the sounds are coming from, but if one mouth is moving, and the other one isn't, we just assume that the sound is coming from what we can see.

Another visual capture illusion is pretty simple. Show a person an object that goes right to left. Have them hear a sound that goes left to right. They should be confused, right? No. They'll hear the sound as moving along with the object, even if it doesn't. Again, people look for the source of the sound — and if they see something that contradicts what they're hearing, they'll automatically adjust things, so that the auditory agrees with the visual. They even take over language. In this clip, you see a person saying "fa," while hearing them say, "ba." Close your eyes, and you hear the "ba" clearly. When you watch the mouth saying "fa," your eyes tell you that you hear "fa."

Visual capture illusions even take over direct sensations. We have internal parts of the brain that monitor what position our body is in. This allows us to perform simple operations without looking at our bodies as we're doing them. When researchers, for example, blocked people from seeing their left hand and asked them to move it in certain ways, they didn't have much trouble. When the subjects sat at a table with a mirror perpendicular to the middle of their body, things got more complicated. The mirror again blocked out their view of their left hand, but it reflected their right hand, making an image that made it seem as if they were looking at their left hand. The researchers then had them perform those same series of functions. Suddenly the visual data kicked in. Although the people felt their left hand move — and they were moving it themselves — they saw a left hand that was standing still. This totally confused their senses, and made them ridiculously clumsy with a hand that they controlled.

We believe the world is as we see it, and for the most part, we're right. But occasionally, just occasionally, we're wrong. And when we are, hopefully we find out before a train hits us.